Document EE 200100111 discloses a separator for separating solid particles from a vapour-gas mixture, wherein the separator comprises a dust chamber (main body) with refractory lining placed on its internal surface, an inlet for the vapour-gas mixture coming from a rotary kiln to the main body of the dust chamber, first and second-stage cyclones placed inside the main body of the dust chamber, and an outlet for separated semi-coke particles.
For process reasons the vapour-gas mixture shall not condense during contact with the walls of the vessels. Therefore the wall temperature has to be maintained above 500° C. and the walls shall resist the abrasive fine solid particles. In case of condensation, the fine solids and the condensed gas-vapour would form agglomerations which build up at the walls and openings. This may lead to massive operation disturbance or even to a total failure of the process.
Document WO 2009/030241 A1 discloses a separator (dust chamber) for separating solid particles from vapour-gas mixture comprising a main body with refractory lining placed on its internal surface and first and second-stage cyclones placed outside the main body of the dust chamber. The main body of dust chamber has a uniform diameter in its full height, where in the middle of the cylindrical body an inlet for a vapour-gas mixture containing semi-coke particles and in the bottom of the cylindrical body an outlet for removal of semi-coke particles is provided.
Despite of the improvements and construction changes, the separator of solid particles from vapour-gas mixture described in document WO 2009/030241 has certain shortcomings that decrease the separation efficiency and availability of the separator. Problems are caused by the internal refractory lining because it has to be resistant to the components and the temperature of the vapour-gas mixture. The temperature of the vapour-gas mixture is about 480 to 520° C. and it contains solid particles, which cause wear of the refractory lining, and corrosive elements, e.g. sulphur. Due to the porosity of the refractory material and potential cracks caused by heat cycles the vapour-gas mixture penetrate the refractory layers, which causes the hydrocarbon vapour in the vapour-gas mixture to condense on the inside metal wall of the main body of the dust chamber. This condensation is due to the fact that the temperature of the refractory lining and the metal surface is always lower than the temperature of the vapour-gas mixture. Solid particles separated from the vapour-gas mixture stick to these surfaces and lead to considerable material layers. Such layers need to be removed frequently during plant shut downs because they have a negative influence on the separation efficiency of the device. Such interruptions of the plant operation considerably reduce the plant availability.
Another disadvantage of the above-described separator is the fact that the small particles fraction, which is separated from the vapour-gas in the first and second stage cyclones, is discharged to the lower part of the main body of the dust chamber. From there some part of fine semi-coke particles (dust particles) will be entrained again into the vapour-gas mixture streams entering the dust chamber. A dust circuit is built up, which decreases the separation efficiency of the whole device.